One thing that I have learned is that my electric brake controller does not respond well at low speeds. When going slowly down steep hills with limited traction and especially if there is a turn involved I need to keep a hand on the manual override to keep from getting out of control.
You did not give us any information on what the transition looks like going from 16% to level. I have a steeper slope in my driveway and have never had an issue with anything dragging but then I have about a 100ft long transition zone. Getting enough traction to pull a trailer up the slope can be issue, especially if it is covered in loose gravel instead with no fine materials to hold the gravel in place. If you have a 4wd truck and it weighs at least half as much as your trailer and the surface is a well packed mix you should be OK, as long as there hasn't been any hard rain to cause washouts. I keep my 4000lb boat at the top of the hill and have pulled it up my slope that is about 18% with a two wheel drive van or truck many times but a running start is very helpful. My new 4wd truck does make it nicer. I keep my 12,000lb trailer at the bottom of the hill for traction reasons. Before you start up have a plan of what to do if traction fails you and keep your hand on the brake controller.